A control method for rough rolling head of a bar

Abstract

The application provides a control method for bar rough rolling wedge head steel piling, analyzes the causes of bar rough rolling wedge head steel piling, and clearly defines the influencing factors that need to be designed and controlled, so as to design process parameters from four aspects of rough rolling mill set entrance guide opening degree, rough rolling mill set roller roughness, rolling piece biting speed and roller cooling water opening time. The application solves the problem of rough rolling wedge head steel piling, reduces the production accidents of the bar, and ensures the smooth production.

Description

Technical Field

[0001] This application relates to the technical field of steel rolling production, and more specifically, to a method for controlling the stacking of steel bars during rough rolling. Background Technology

[0002] Rough rolling is one of the important pieces of equipment in a high-speed bar production line. Its main function is to reduce the cross-section of the rolling mill so that subsequent units can continue rolling.

[0003] Steel piling up at the roughing mill is a common problem faced by domestic bar production lines. Currently, the measures taken by similar domestic production lines generally involve controlling the Mn / s ratio of the rolling mill composition, preventing raw material from becoming square, and controlling defects such as mill holes and cracks. YB / T4827-2020, "Continuous Casting Mills and Rectangular Billets for Hot-Rolled Steel Bars," which came into effect on April 1, 2021, stipulates that for nominal side lengths > 140-180 mm, the difference in diagonal lengths should be ≤ 7 mm. This difference in diagonal lengths is also known as "squareness." According to relevant literature, similar domestic steel rolling production lines require "squareness" to be ≤ 10 mm. If "squareness" exceeds 10 mm, it will cause steel piling up at the roughing mill. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for controlling the splitting and bulging of steel in rough rolling of bar stock, which can control the problem of crack propagation inside the rolling mill during the rolling process, fundamentally solve the cracking and splitting defects that occur during rough rolling, solve the production problem of splitting and bulging of steel in rough rolling, and improve rolling efficiency and product quality.

[0005] The embodiments of this application are implemented as follows:

[0006] This application provides a method for controlling the stacking of steel at the split end of rough-rolled bar stock, characterized by the following steps:

[0007] Step a, determine the factors affecting the splitting and stacking of steel in the roughing mill, specifically including: the opening degree of the inlet guide of the roughing mill, the roughing mill roll roughness, the bite speed of the rolled piece, and the opening time of the roll cooling water.

[0008] Step b, the roughing mill group includes six mills, namely No. 1 mill, No. 2 mill, No. 3 mill, No. 4 mill, No. 5 mill and No. 6 mill, and designs are carried out for various influencing factors for different mills.

[0009] In some optional implementations, when designing the opening degree of the inlet guide of the roughing mill, the inlet guide is used to guide the trend of the bar stock. If the opening degree of the inlet guide is too small, there will be a steel jamming phenomenon. If the opening degree of the inlet guide is too large, it will cause the stock to deviate. Therefore, the opening degree of the inlet guide of the No. 1 mill is controlled.

[0010] In some alternative implementations, the roughness design for the roughing mill rolls is achieved by overlaying welds along the length of the roll body on the surface of the No. 1 mill roll.

[0011] In some alternative implementations, the rolling speeds of each mill are designed for the bite speed of the workpiece as follows:

[0012] The rolling speeds of the No. 1 rolling mill are 0.438 m / s to 0.644 m / s, the No. 2 rolling mill is 0.564 m / s to 0.830 m / s, the No. 3 rolling mill is 0.779 m / s to 1.145 m / s, the No. 4 rolling mill is 1.042 m / s to 1.532 m / s, the No. 5 rolling mill is 1.348 m / s to 1.982 m / s, and the No. 6 rolling mill is 1.727 m / s to 2.540 m / s.

[0013] In some alternative implementations, when designing the roll cooling water start-up time, the water of the Nth mill is turned on when the workpiece enters the N+1th mill, where N is a value of 1-5.

[0014] In some optional implementations, the specific timing of the roll cooling water activation is as follows:

[0015] When the No. 2 rolling mill bites the steel for 0.7-1.1 seconds, the cooling water for the work rolls of the No. 1 rolling mill is turned on. When the No. 3 rolling mill bites the steel for 0.6-0.8 seconds, the cooling water for the work rolls of the No. 2 rolling mill is turned on. When the No. 4 rolling mill bites the steel for 0.4-0.6 seconds, the cooling water for the work rolls of the No. 3 rolling mill is turned on. When the No. 5 rolling mill bites the steel for 0.3-0.5 seconds, the cooling water for the work rolls of the No. 4 rolling mill is turned on. When the No. 6 rolling mill bites the steel for 0.25-0.35 seconds, the cooling water for the work rolls of the No. 6 rolling mill is turned on. When the No. 6 rolling mill bites the steel for 0.2-0.3 seconds, the cooling water for the work rolls of the No. 6 rolling mill is turned on.

[0016] In some alternative implementations, the opening of the No. 1 mill inlet guide is 188–194 mm.

[0017] In some alternative implementations, the weld overlay height is less than 2 mm, and the electrode spacing is 80-120 mm.

[0018] The beneficial effects of this application are as follows: The method for controlling the splitting and accumulating of steel in the rough rolling of bars provided by this application can control the problem of crack propagation inside the rolling mill during the rolling process, fundamentally solve the cracking and splitting defects that occur during the rough rolling process, solve the production problem of splitting and accumulating steel in the rough rolling, improve rolling efficiency and product quality, prevent scrap steel from being produced on the rough rolling channel, and achieve the purpose of reducing scrap steel and stabilizing production. At the same time, under the existing production conditions, it can meet the requirements without making major changes to the production equipment and process flow, is easy to operate, and has good performance. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown herein can generally be arranged and designed in various different configurations.

[0020] Therefore, the following detailed description of the embodiments provided in this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0021] It should be noted that similar labels and letters indicate similar items; therefore, once an item is defined, it does not need to be further defined and explained subsequently.

[0022] The features and performance of this application will be further described in detail below with reference to the embodiments.

[0023] This invention proposes a method for controlling the stacking of steel at the split end of rough rolling bar stock, comprising the following steps:

[0024] 1. Determine the factors affecting the splitting and stacking of bar stock in roughing mill, specifically including: the opening degree of the inlet guide of the roughing mill, the roughing mill roll roughness, the bite speed of the rolled piece, and the start time of the roll cooling water.

[0025] 2. The roughing mill unit consists of six mills: No. 1, No. 2, No. 3, No. 4, No. 5 and No. 6. The design of various influencing factors is carried out for each mill.

[0026] A detailed analysis of the mechanisms influencing the steel stacking at the split end of rough-rolled bars:

[0027] (1) Opening degree of the inlet guide of the roughing mill:

[0028] The opening degree of the inlet guide of the No. 1 mill in the roughing mill is controlled because the inlet guide guides the movement of the mill. In actual production, if the guide opening degree is too small, steel jamming will occur. Steel jamming will cause excessive local cooling of the mill by the mill cooling water. When rolling continues, defects such as cracks and holes inside the mill will not be compressed, and at the same time, the expansion of internal defects will be aggravated. After the defects at the head of the rolled piece are magnified, steel will easily accumulate at the exit of the No. 2 mill and the inlet of the No. 4-6 mills. If the guide opening degree is too large, the guiding function of the guide will fail, which will cause the rolled piece to deviate and is prone to impacting the inlet guide of the No. 2 mill and accumulating steel. Therefore, the opening degree of the inlet guide of the No. 1 mill must be precisely controlled.

[0029] (2) Roughness of the roughing mill rolls:

[0030] Due to the large reduction in bar roughing, the lack of descaling on the mill surface, and the high temperature, iron oxide scale is easily generated. The combined effect of these factors results in a low coefficient of friction between the mill and the rolls, making slippage accidents prone to occur during the roughing stage. When slippage occurs, the mill head is blackened by the mill cooling water. During the continued rolling process, the uneven rolling extension caused by the poor temperature uniformity between the upper and lower parts of the mill leads to the expansion of internal cracks. Since the head area is in a state of detension during rolling, cracking defects are easily formed. Different crack sizes lead to different degrees of cracking. Therefore, the No. 1 mill rolls need to be designed with roughness.

[0031] (3) Biting speed of the rolled piece:

[0032] Low mill bite speed results in prolonged exposure of the mill to air and significant temperature drop. Conversely, excessively high bite speed leads to slippage and difficulty in biting. Therefore, on-site monitoring has revealed that controlling the mill bite speed is another key factor in controlling the roughing mill splitting.

[0033] (4) Roll cooling water start-up time:

[0034] Because the cooling water is turned on before the mill passes the stand, the water stays on the upper surface of the strip for a long time, resulting in uneven cooling between the upper and lower surfaces of the mill. The temperature of the lower surface is higher, and the elongation during rolling is greater. This causes asymmetrical biting between the upper and lower surfaces of the mill, which can easily lead to strip warping.

[0035] Controlling the cooling water in the rolls is crucial because it affects the roll body and grooves, primarily aiming to reduce their temperature, slow down groove wear, extend groove lifespan, and decrease roll replacement frequency. During the rolling process, both horizontal and vertical mills retain some cooling water on the upper surface of the work rolls. This creates a temperature difference between the upper and lower surfaces. During rolling deformation, the lower surface has a greater elongation than the upper surface, making it difficult to close internal defects and increasing the risk of splitting and piling up steel at the mill head. Therefore, it is necessary to control the cooling water at the mill head during the biting process in the roughing mill.

[0036] The technical solution adopted by this invention to solve its technical problem is as follows:

[0037] 1. During the stage of controlling the opening degree of the inlet guide of the roughing mill, the opening degree of the inlet guide of the No. 1 mill is precisely controlled. Specifically, the opening degree of the inlet guide of the No. 1 mill is 188-194mm.

[0038] 2. In the stage of increasing the roughness of the No. 1 rolling mill roll, strip welding is carried out on the surface of the roll along the length of the roll body. The welding height is controlled within 2mm, and the welding spacing between the strip welding is 80-120mm.

[0039] 3. In the stage of controlling the bite speed of the rolled piece, specifically, the rolling speeds of each rolling mill are as follows:

[0040] The rolling speeds of the No. 1 rolling mill are 0.438 m / s to 0.644 m / s, the No. 2 rolling mill is 0.564 m / s to 0.830 m / s, the No. 3 rolling mill is 0.779 m / s to 1.145 m / s, the No. 4 rolling mill is 1.042 m / s to 1.532 m / s, the No. 5 rolling mill is 1.348 m / s to 1.982 m / s, and the No. 6 rolling mill is 1.727 m / s to 2.540 m / s. Further, the preferred rolling speeds for each mill are 0.541 m / s, 0.697 m / s, 0.962 m / s, 1.287 m / s, 1.665 m / s, and 2.133 m / s, respectively.

[0041] 4. In the design stage of the roll cooling water start-up time, when the workpiece enters the N+1th rolling mill, the water of the Nth rolling mill is turned on, and the value of N is 1-5.

[0042] The specific start-up times for the cooling water of each roll are as follows:

[0043] When the No. 2 mill bites the steel for 0.7-1.1 seconds, the cooling water for the work rolls of the No. 1 mill is turned on. When the No. 3 mill bites the steel for 0.6-0.8 seconds, the cooling water for the work rolls of the No. 2 mill is turned on. When the No. 4 mill bites the steel for 0.4-0.6 seconds, the cooling water for the work rolls of the No. 3 mill is turned on. When the No. 5 mill bites the steel for 0.3-0.5 seconds, the cooling water for the work rolls of the No. 4 mill is turned on. When the No. 6 mill bites the steel for 0.25-0.35 seconds, the cooling water for the work rolls of the No. 5 mill is turned on. When the No. 6 mill bites the steel for 0.2-0.3 seconds, the cooling water for the work rolls of the No. 6 mill is turned on. This achieves the goal of no roll cooling when the head of the rolled piece bites into the mill stand.

[0044] Example 1

[0045] Taking finished product specifications R12 / 14 / 20 / 25 / 28 / 32mm and rolling 104,825 tons as an example:

[0046] ① Control the opening degree of the inlet guide of No. 1 rolling mill: 194mm.

[0047] ②Increase the roughness of the No. 1 rolling mill rolls: weld height 2mm, weld spacing between strips 85mm.

[0048] ③ Control the bite speed of the rolled piece: The rolling speeds of each mill in the roughing mill are 0.44m / s, 0.57m / s, 0.85m / s, 1.1m / s, 1.4m / s, and 1.8m / s.

[0049] ④ Control the cooling water of the rolls: After the No. 2 rolling mill bites the steel for 0.75 seconds, start the cooling water of the No. 1 rolling mill work rolls; after the No. 3 rolling mill bites the steel for 0.65 seconds, start the cooling water of the No. 2 rolling mill work rolls; after the No. 4 rolling mill bites the steel for 0.45 seconds, start the cooling water of the No. 3 rolling mill work rolls; after the No. 5 rolling mill bites the steel for 0.35 seconds, start the cooling water of the No. 4 rolling mill work rolls; after the No. 6 rolling mill bites the steel for 0.25 seconds, start the cooling water of the No. 5 rolling mill work rolls; after the No. 6 rolling mill bites the steel for 0.2 seconds, start the cooling water of the No. 6 rolling mill work rolls.

[0050] Results: During this month-long production run, 39,512 steel bars were rolled without any issues of steel splitting or piling during rough rolling.

[0051] Example 2

[0052] Taking finished product specifications R12 / 14 / 16 / 25 / 28mm and a rolling volume of 62,364 tons as an example:

[0053] ① Control the opening degree of the inlet guide of No. 1 rolling mill: 192mm.

[0054] ② Increase the roughness of the No. 1 rolling mill rolls: the weld overlay height is 2mm, and the weld overlay spacing between strips is 95mm.

[0055] ③ Control the bite speed of the rolled piece: The rolling speeds of each mill in the roughing mill are 0.49m / s, 0.62m / s, 0.91m / s, 1.29m / s, 1.51m / s, and 2.12m / s.

[0056] ④ Control the cooling water of the rolls: 0.8s after the No. 2 rolling mill bites the steel, the cooling water of the No. 1 rolling mill's work rolls is turned on; 0.7s after the No. 3 rolling mill bites the steel, the cooling water of the No. 2 rolling mill's work rolls is turned on; 0.5s after the No. 4 rolling mill bites the steel, the cooling water of the No. 3 rolling mill's work rolls is turned on; 0.4s after the No. 5 rolling mill bites the steel, the cooling water of the No. 4 rolling mill's work rolls is turned on; 0.3s after the No. 6 rolling mill bites the steel, the cooling water of the No. 5 rolling mill's work rolls is turned on; 0.25s after the No. 6 rolling mill bites the steel, the cooling water of the No. 6 rolling mill's work rolls is turned on.

[0057] Results: During this production run of 18 days, 23,507 steel bars were rolled without any issues of steel splitting or piling up during rough rolling.

[0058] Example 3

[0059] Taking a finished product specification of R16 / 18mm and a rolling volume of 83,272 tons as an example:

[0060] ① Control the opening degree of the inlet guide of No. 1 rolling mill: 190mm.

[0061] ② Increase the roughness of the No. 1 rolling mill rolls: the weld overlay height is 2mm, and the weld overlay spacing between strips is 110mm.

[0062] ③ Control the bite speed of the rolled piece: The rolling speeds of each mill in the roughing mill are 0.52m / s, 0.69m / s, 0.98m / s, 1.35m / s, 1.67m / s, and 1.29m / s.

[0063] ④ Control the cooling water of the rolls: 0.9s after the No. 2 rolling mill bites the steel, the cooling water of the No. 1 rolling mill's work rolls is turned on; 0.75s after the No. 3 rolling mill bites the steel, the cooling water of the No. 2 rolling mill's work rolls is turned on; 0.55s after the No. 4 rolling mill bites the steel, the cooling water of the No. 3 rolling mill's work rolls is turned on; 0.4s after the No. 5 rolling mill bites the steel, the cooling water of the No. 4 rolling mill's work rolls is turned on; 0.3s after the No. 6 rolling mill bites the steel, the cooling water of the No. 5 rolling mill's work rolls is turned on; 0.25s after the No. 6 rolling mill bites the steel, the cooling water of the No. 6 rolling mill's work rolls is turned on.

[0064] Results: During this production run of 16 days, 31,388 steel bars were rolled without any issues of steel splitting or piling up during rough rolling.

[0065] Example 4

[0066] Taking finished product specifications R16 / 20 / 25 / 28 / 32mm and a rolling volume of 59,729 tons as an example:

[0067] ① Control the opening degree of the inlet guide of No. 1 rolling mill: 188mm.

[0068] ② Increase the roughness of the No. 1 rolling mill rolls: the weld overlay height is 2mm, and the weld overlay spacing between strips is 120mm.

[0069] ③ Control the bite speed of the rolled piece: The rolling speeds of each mill in the roughing mill are 0.61m / s, 0.81m / s, 1.12m / s, 1.47m / s, 1.91m / s, and 2.48m / s.

[0070] ④ Control the cooling water of the rolls: 1.0s after the No. 2 rolling mill bites the steel, the cooling water of the No. 1 rolling mill's work rolls is turned on; 0.8s after the No. 3 rolling mill bites the steel, the cooling water of the No. 2 rolling mill's work rolls is turned on; 0.6s after the No. 4 rolling mill bites the steel, the cooling water of the No. 3 rolling mill's work rolls is turned on; 0.45s after the No. 5 rolling mill's work rolls bite the steel, the cooling water of the No. 4 rolling mill's work rolls is turned on; 0.35s after the No. 6 rolling mill bites the steel, the cooling water of the No. 6 rolling mill's work rolls is turned on; 0.3s after the No. 6 rolling mill bites the steel, the cooling water of the No. 6 rolling mill's work rolls is turned on.

[0071] Results: This production run lasted 11 days, producing 22,514 steel bars, and no issues with steel splitting or piling up occurred during the rough rolling process.

Claims

1. A method for controlling the stacking of steel at the split end of rough rolling bar stock, characterized in that, Includes the following steps: Step a, determine the factors affecting the splitting and stacking of steel in the roughing mill, specifically including: the opening degree of the inlet guide of the roughing mill, the roughing mill roll roughness, the bite speed of the rolled piece, and the opening time of the roll cooling water. Step b, the roughing mill group includes six mills, namely mill No. 1, mill No. 2, mill No. 3, mill No. 4, mill No. 5 and mill No.

6. The design of various influencing factors is carried out for each mill: When designing the inlet guide opening of the roughing mill, the inlet guide opening of the No. 1 mill is controlled; when designing the roughing mill roll roughness, welding is performed along the length of the roll body on the surface of the No. 1 mill roll; when designing the workpiece bite speed, the rolling speeds of each mill are as follows: The rolling speeds of the No. 1 rolling mill are 0.438 m / s to 0.644 m / s, the No. 2 rolling mill is 0.564 m / s to 0.830 m / s, the No. 3 rolling mill is 0.779 m / s to 1.145 m / s, the No. 4 rolling mill is 1.042 m / s to 1.532 m / s, the No. 5 rolling mill is 1.348 m / s to 1.982 m / s, and the No. 6 rolling mill is 1.727 m / s to 2.540 m / s. When designing the roll cooling water start-up time, the water supply to the Nth rolling mill is turned on when the workpiece enters the N+1th rolling mill, where N is a value of 1-5.

2. The method for controlling the stacking of bar rough-rolled split ends according to claim 1, characterized in that, The specific start-up time for the roll cooling water is as follows: When the No. 2 rolling mill bites the steel for 0.7-1.1 seconds, the cooling water for the work rolls of the No. 1 rolling mill is turned on. When the No. 3 rolling mill bites the steel for 0.6-0.8 seconds, the cooling water for the work rolls of the No. 2 rolling mill is turned on. When the No. 4 rolling mill bites the steel for 0.4-0.6 seconds, the cooling water for the work rolls of the No. 3 rolling mill is turned on. When the No. 5 rolling mill bites the steel for 0.3-0.5 seconds, the cooling water for the work rolls of the No. 4 rolling mill is turned on. When the No. 6 rolling mill bites the steel for 0.25-0.35 seconds, the cooling water for the work rolls of the No. 6 rolling mill is turned on. When the No. 6 rolling mill bites the steel for 0.2-0.3 seconds, the cooling water for the work rolls of the No. 6 rolling mill is turned on.

3. The method for controlling the stacking of bar rough-rolled split ends according to claim 1 or 2, characterized in that, The inlet guide is used to guide the movement of the bar stock. If the opening of the inlet guide is too small, steel will be stuck. If the opening of the inlet guide is too large, the stock will deviate. The opening of the inlet guide of the No. 1 mill is 188-194mm.

4. The method for controlling the stacking of bar rough-rolled split ends according to claim 3, characterized in that, The weld overlay height is within 2mm, and the electrode spacing is 80-120mm.